This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 101 06 516.7, filed on Feb. 13, 2001, the entire disclosure of which is incorporated herein by reference.
The invention relates to a method and an apparatus for simulating variable accelerations between 0 g and 1 g (where xe2x80x9cgxe2x80x9d is Earth""s gravitational acceleration), and especially for simulating reduced gravity conditions, for example as exist on the surface of planets such as Mars. The invention especially relates to carrying out such simulations using a parabolic flight path of an aircraft.
In order to simulate, test and evaluate the operation of devices, equipment and processes that are to operate on the surface of the planet Mars, in the scope of a manned or unmanned mission, it is necessary to simulate the environmental conditions prevailing on Mars as completely and accurately as possible here on Earth. While the atmospheric or environmental conditions (e.g. temperature, gas composition, pressure, etc.) prevailing on the surface of Mars can be relatively easily simulated in suitable test chambers, it is rather problematic to simulate the small gravitational acceleration of only 3.72 m/s2, i.e. approximately ⅓ g (or somewhat more accurately xe2x85x9c g), which prevails on the surface of Mars.
The standard gravitational acceleration at the Earth""s surface, namely g, is approximately 9.81 m/s2. Thus, any gravitational acceleration condition deviating from the Earth""s gravitational acceleration g will require simulation efforts that overcome or interact with the Earth""s normal gravitational field. Various methods for such simulation of different accelerations are known. For example, it is known to use centrifuges to generate accelerations, i.e. simulated gravitational conditions, greater than Earth""s normal gravitational acceleration g. In such centrifuge methods, the artificial elevated acceleration can be established and maintained for essentially any desired duration. These centrifuge methods cannot, however, realize accelerations less than 1 g, because they always involve superimposing an additional acceleration on the basic 1 g gravitational acceleration. Thus, such methods are not suitable for the field of application of interest for the present invention.
For simulating accelerations between 0 and 1 g, it is also known to use drop towers or fall towers, from which test specimens or test capsules can be dropped toward the Earth under the influence of the Earth""s gravitational acceleration, with a selected braking or resistance against the acceleration. In this manner, weightless (0 g) conditions or reduced gravity conditions can be achieved for a duration of up to approximately 5 seconds. For example, such drop towers or fall towers can realize a residual weight of ⅓ g, by braking or decelerating the falling test capsule corresponding to an acceleration of ⅔ g against or contrary to the Earth""s acceleration toward the Earth. This braking can be carried out either actively or passively, for example by means of a counterweight connected to the test capsule by a cable over a roller or pulley, so that the counterweight is lifted while the test capsule falls. For an acceleration of ⅓ g, the fall times that can be achieved, e.g. for a tower height and falling distance of 100 m, are thus approximately 5.5 seconds. Trying to achieve longer fall times with a higher tower or the like is impractical. Moreover, the test capsule released from such a drop or fall tower typically must be subjected to a rather hard or intensive braking phase with a considerable braking shock at the end of the fall time. Such a braking shock exerts a correspondingly strong deceleration onto the test capsule, which can damage any equipment in the test capsule and could endanger test personnel if they were to be present in the test capsule.
A further possibility for generating accelerations between 0 and 1 g is seen in the use of so-called atmospheric drop capsules or fall capsules, which are dropped from an aircraft or the like at a high altitude and which generally include an active arrangement for compensating the atmospheric resistance. It is theoretically conceivable, but not known to exist yet in the prior art, to equip such fall capsules with an active braking system so that they fall toward the Earth with an acceleration corresponding to ⅔ g so as to experience a residual weight of ⅓ g. For such a fall capsule being dropped from an elevation of 8000 meters, the desired acceleration of ⅓ g could be achieved for a fall duration of approximately 40 seconds. It is further significant that manned atmospheric fall capsules have not yet become known in the prior art, presumably because their realization would be extremely complicated and costly due to the safety requirements that would have to be met.
It is further known to carry out a parabolic flight path with an appropriately equipped aircraft for achieving weightlessness, or so-called 0 g (zero g) conditions, for a duration of up to approximately 25 seconds. In this context, the aircraft flies on a so-called parabolic projectile trajectory, namely the trajectory path on which a non-propelled projectile would travel without any air resistance.
In view of the above, it is an object of the invention to provide a method of the type generally last mentioned above, using a parabolic flight path of an aircraft to achieve the simplest and most effective simulation of reduced gravity conditions, for example such as exist on the surface of Mars. It is another object of the invention to provide an apparatus or system for carrying out such a method. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a method for achieving variable accelerations greater than 0 g and less than 1 g, and especially for simulating the gravitational conditions on the surface of Mars, by flying an aircraft (and particularly a high capacity transport or cargo aircraft) on a parabolic flight path, with an acceleration relative to Earth that is equivalent to a falling acceleration of which the difference relative to the Earth""s gravitational acceleration corresponds to the acceleration to be simulated.
The above objects have further been achieved according to the invention in a system for simulating a selected acceleration greater than 0 g and less than 1 g, comprising a transport aircraft having a payload space equipped with a test chamber that is movably mounted therein in such a manner, so that the center of gravity of the test chamber automatically or self-actingly is adjustable and orientable in the direction of the momentary effective residual acceleration.
According to the invention, an otherwise generally conventional transport or cargo aircraft having a sufficiently large cargo space or general payload space, is equipped with a test chamber that is movably arranged therein so that the test chamber can orient itself with respect to the effective residual acceleration acting thereon. This aircraft is then flown along a parabolic flight path, which especially corresponds to an external fall acceleration of ⅔ g, so that an effective residual acceleration of ⅓ g oriented toward the surface of the Earth remains effective as a residual weight on the test chamber and any test object arranged therein. In other words, the test chamber and any test objects arranged and supported therein will experience a gravitational condition corresponding to ⅓ g. The inventive articulated or jointed suspension of the test chamber thereby serves to ensure that the residual weight in the test chamber is always oriented in a direction toward the center of the Earth, independently of the actual momentary flight attitude or orientation of the aircraft during its parabolic flight.
The duration of the ⅓ g phase of the parabolic flight path depends on the height of this flight path. With a height difference of 3000 meters between the apex or zenith of the parabola and the starting altitude as well as the end altitude, this time duration will amount to approximately 55 seconds, while the aircraft""s vertical speed at the beginning and the end of the parabolic flight path will respectively be about 180 m/s (upward and downward respectively). The braking or pull-out phase of the flight is carried out in a manner analogous to the known 0 g parabolic flights, and thus does not generate excessive g forces or cause any other problems for the equipment or personnel located in the test chamber.
The invention makes it possible to achieve not only an acceleration of ⅓ g, but also any desired or selected acceleration value greater than 0 g and less than 1 g. Such acceleration or gravity conditions can be established and maintained as a test acceleration for a duration of about 60 seconds, so that various present-day devices and methods or processes can be operated to carry out the intended experiments or tests. Moreover, the duration and the gravity conditions are such that persons can be present in a suitably equipped test chamber before, during and after the test. The deceleration (or braking acceleration) at the end of the end of the parabolic flight phase can be maintained at a value below about 2 g, so as to avoid harm or discomfort to the persons involved in the test, and to avoid damage to the equipment. The aircraft may then return to the ground, or another test phase can be almost immediately repeated.